This invention relates to path prediction for a motor vehicle collision warning system.
The present construction is directed towards a motor vehicular collision warning system which includes a scanned beam sensor, a signal processor, and a vehicle interface system that initiates warnings to the driver or adaptively controls the vehicle. In this forward looking collision warning system, the sensor is designed to project a narrow beam of energy toward objects in the forward field of view. The detection system is suitable for collision warning for notifying a driver of an impending collision or initiating evasive action to avoid a collision or providing adaptive cruise control, braking, and the like that actively adjust the vehicle speed to maintain a time headway relative to the closest in path vehicle.
It is known to detect the distance between a vehicle and another in path vehicle and warn a driver so as to avoid collision between the vehicles. To provide such control, it is necessary to discriminate between the closest in path vehicle and the plurality of other vehicles that may be ahead of the vehicle having collision warning capability. One technique for providing discrimination includes a radar unit that emits a radar wave forward of the vehicle so as to detect objects existing in front of the vehicle. Using this technique, it is possible to detect the closest in path vehicle from other vehicles.
A common approach for forward looking collision warning systems is to detect objects in the forward field of view based upon vehicle size criteria. One of the reasons for using this technique is the result of the difficulty in obtaining high resolution with known collision warning systems. However, the known techniques for xe2x80x9cmacroxe2x80x9d detection and discrimination can result in false alarms that affect the driver""s perception of the system and can potentially negate the driver""s reliance on the system thereby limiting the overall accident prevention effectiveness of the system.
Another issue related to object discrimination is the knowledge of the predicted path for the vehicle. This is critical in the classification of in path and out of path objects. Path prediction may be performed using a separate vision based or location based sensor system which adds to the overall cost and complexity of the complete system.
Therefore, it is an object of the present invention to avoid the aforementioned disadvantages and problems associated with existing vehicular collision warning systems.
In accordance with this invention, data from a forward looking radar system is used to predict the path of the roadway in front of a vehicle. Reflections from roadside objects such as trees, bushes, light poles, fire hydrants, and the like are extracted. The data is then used to define a linear feature edge for the roadway. After the feature edge of the roadway is determined, the predicted path of the vehicle can be determined using this information as well as information regarding the vehicle trajectory.
The present invention provides improved performance for a forward looking collision warning system by extraction and path prediction using small amplitude, non-vehicular, object data. The scene is processed by extracting the small amplitude, non-vehicular, object data. Objects are then combined to form a linear feature edge that is equivalent to the roadway feature edge. Examples of the small amplitude, non-vehicular, objects include telephone poles, streetlights, trees, bushes, curbs, fences, and the like. These small amplitude, non-vehicular, objects follow the path of the roadway. By combining them in linear, straight or curved, trajectories, the predicted path of the roadway can be estimated. Further, a comparison of the offset from the detected feature edge and the center line or trajectory of the vehicle allows the predicted forward path to be determined. The feature edge is used to exclude objects that would not represent a collision threat such as those at the entry and exit points of curves which are normally problematic with respect to providing false warnings to the driver. The predicted forward path also includes the lane of travel of the vehicle when adaptive cruise control is desired.
The present invention utilizes a high resolution imaging type forward looking radar system to extract secondary objects from the received data. The radar apparatus is provided with a rotatable antenna structure such as a slotted wave guide antenna. The antenna is driven to oscillate back and forth at an angle of 10xc2x0 or less in each direction. A transceiver is coupled to the antenna and the antenna passes transmitted and reflected radar signals to and from a target as it is oscillated back and forth. The scanned signals are directed to a processor and then to a vehicle interface system for initiating warnings to the driver or adaptively controlling the vehicle.
Thus, the present invention predicts the path of the roadway in front of the vehicle by extracting scene data from the radar return. The processed data defines a linear feature edge which is combined with information regarding the vehicle trajectory to determine the predicted path of the vehicle.
The foregoing and other advantages and features of the invention will be more apparent from the following description when taken in connection with the accompanying drawings.